Stroke-adjusting and rebound-damping device for high-speed printer hammers



Dec. 31, 1968 G. PONZANO 3,418,928

STROKE-ADJUSTING AND REBOUND-DAMPING DEVICE FOR HIGH-SPEED PRINTER HAMMERS Filed Sept. 30. 1966 -FIG.2-

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United States Patent 3,418,928 STROKE-ADJUSTING AND REBOUND-DAMPING DEVICE FOR HIGH-SPEED PRINTER HAMMERS Gianluigi Ponzano, Via Aldisio 14, Ivrea, Turin, Italy Filed Sept. 30, 1966, Ser. No. 583,382 4 Claims. (Cl. 101-93) ABSTRACT OF THE DISCLOSURE A device for adjusting the stroke and preventing the rebound of a high speed print hammer utilizing the shock absorbing qualities of a block of plastic material through which the stop member is threaded.

The present invention relates to a device for adjusting the forward stroke and damping the rebounds of the backward stroke of the hammer in a high speed printer.

The prior art structure in high speed printers of the type under consideration substantially contains typewheels on which the characters appear in relief and are disposed in adjacent columns forming circular rings, the print hammers, for example one for each column, wherein the hammers are actuated by electromagnets controlled by proper electrical circuits and drive a continuous sheet of print receiving paper and one of carbon paper, or an inked ribbon against the typewheel, thereby causing the selective printing of a character. Immediately thereafter, the hammers are brought back to the rest position by a restoring spring.

In order to obtain a perfectly aligned print, it is necessary to individually adjust the operating time of each one of the electromagnets to compensate for the small differences existing between the time constants of the different control circuits, and between the operating speed of the individual electromagnets so that the instant of the impact of each one of the hammers, for all hammers, corresponds exactly to the desired angular position of the typewheel.

This is obtained by adjusting the rest position of each individual hammer, While at rest, by changing the air gap between the armature and the pole pieces of the electromagnets.

It is therefore necessary that the rest position of the hammers be adjustable and, when adjusted, be perfectly set and stable.

It is moreover necessary, that there be no vibrations or rebounds of the hammer when it is being brought back to its rest position so that the state of the hammer when receiving a new actuating impulse will not be influenced by previous impulses.

The same applies to those high speed printers Where the characters are carried by a chain or any other linearly moving device and in general to every case where the printing is obtained by driving the paper against a rapidly moving character.

It is therefore an object of the present invention to provide a device which ensures, conjointly precise adjusting means for the rest position of the hammers, and efficient damping of the energy inherent in the hammer at the end of the return stroke. This object is attained by using a slidable stop member which is maintained in its rest position by an elastical force greater than the force due to the restoring spring.

These and other features of the invention will become apparent from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawing wherein:

FIGURE 1 is a print hammer assembly showing a plurality of print hammers utilizing the adjustable rebound damping device and hammer rest positioning device embodying the invention.

FIGURE 2 is a view partially in section, of the rebound damping structure as utilized with the individual hammers of the module in FIGURE 1.

The print hammer 1, having the shape and disposition shown in the figure, is provided with a hardened steel piston 2, whose lower surface rests, in the rest position, on

the terminal portion of a stop mmeber 4, under the action of the restoring spring 3. The stop member 4 has a substantially cylindrical shape and can slide in suitable bores made in the extensions 5 and 6 of frame 7 which frame supports the print device.

A spring washer 8 is located in a groove existing immediately under the terminal surface of the stop member, in contact with the hammer dowel, and a spring 9 having a suitably high rigidity acts on the Washer. This spring, in its rest position, is compressed between the spring Washer 8 and the surface 10 of extension 5.

Under the action of the spring 9, the stop member 4 is tensioned to move upward, but it is prevented from doing so by a block 11, made of plastic material, for instance nylon, or similar substance. The block 11 has a shape substantially parallelepipedal, and it is provided with a longitudinal threaded hole.

The stop member 4 is threaded at its central portion, and is provided with a fixed square head which can be rotated by a suitable wrench. The stop member is screwed into the block 11, and, due to the high coefiicient of friction between the block and the stop member, they are reciprocally and solidly enmeshed. The force of the spring 9 is such, that at rest, it overcomes the force that hammer restoring spring 3 applies to the stop member, and therefore the positions of the stop member, and consequently of the print hammer, are perfectly determined.

If the stop member 4 is screwed into or out from the block 11, using the proper wrench, the position is continuously variable and it is possible to precisely adjust the rest position of the print hammer and consequently the width of the air gap T between the actuating electromagnet and its corresponding armature.

The length of the block 11 is slightly smaller than the distance between the internal surfaces of extensions 5 and 6 of the supporting frame 7, as shown in the figure. Therefor the stop member 4 and the block 11 can perform a small longitudinal stroke, against the action of spring 9. When the print hammer, at the end of the return stroke violently strikes against the stop member 4, its kinetic energy is absorbed by the compression of spring 9, and block 11 is pushed against the lower extension 6 and subsequently spring 9 restores it to the rest position against the upper extension 5. During these movements, because of the friction of the lateral face of block 11 against Wall P, of the internal deformation of the block and the consequence of both impacts against extensions 5 and 6, the acquired energy is dissipated, and the stop member is restored to the rest position, thus also bringing the print hammer, which rests on it, to its rest position without vibration or rebounds.

It should be understood that the foregoing disclosure relates only to a preferred embodiment of the invention and that it is intended to cover all changes and modifications of the example of the invention herein chosen for the purposes of the disclosure which do not constitute departures from the spirit and scope of the invention.

What is claimed is:

1. An adjustable stop member for a high speed print hammer including a base member, a print hammer assembly including a print hammer arm pivotally mounted on said base member, said base member having first and second extension members spaced apart from one another and protruding from said base member, a first bore in said first extension member and a second bore in said second extension member, said first and second bores being coaxial, a plastic block including a threaded bore positioned between said first and second extension members with said threaded bore in coaxial alignment with said first and second bores, a cylindrical shaped member including a central threaded portion complimentary to the thread of said threaded bore of said block, a first end portion and a second end portion at opposing ends of said cylindrical shaped member, said first end portion constituting a stop for the hammer, said second end portion including means for turning said cylindrical shaped member, said cylindrical shaped member having said threaded portion in engagement with said threaded bore, said first end portion protruding from said first extension member remote said block and said second end portion extending into said second extension member, means for tensioning said plastic block against said first extension member and said first end portion of said cylindrical shaped member away from said first extension member, and said first end portion being in contact with and determining the rest position of said print hammer arm.

2. An adjustable stop member for a high speed print hammer as defined in claim 1 wherein said plastic block is shorter than the distance between the closest opposing faces of said first and second extension members.

3. An adjustable stop member for a high speed print hammer as defined in claim 1 wherein said plastic block member is nylon.

4. An adjustable stop member for a high speed print hammer as defined in claim 1 wherein the said plastic block member is nylon and said plastic block is shorter than the distance between the closest opposing faces of said first and second extension members.

References Cited UNITED STATES PATENTS 2,940,385 6/1960 House 10193 3,177,803 4/1965 Antonucci 101-93 3,200,739 8/1965 Antonucci 10193 3,266,418 8/1966 Russo 101-93 WILLIAM B. PENN, Primary Examiner. 

